Compound having the same molecular formula but different number of carbon atoms (alkyl groups) on either side of functional group (i.e., - O - S, - NH, - C = O are called metamers and the phenomenon is called metamerism. Metamerism occurs amongst the members of the same homologus family. the metamerism arises when different alkyl groups are attached to same functional group.
For Example
(1) The following metamers contains the ether functional group. However, they differ by the nature of alkyl groups attached to the oxygen atom.
`H_(3) C - CH_(2) - O - CH_(2) - CH_(3)`
`{:("Diethyl ether"),("or"),("ethoxyethane"):}`
`H_(3)C - O - CH_(2) - CH_(2) - CH_(3)`
`{:("Methylpropyl ether"),("or"),("1-methoxypropane"):}`
`H_(3) C - O - underset(Ch_(3))underset(|)overset(Ch_(3))overset(|)(C H)`
`{:("Isopropyl methyl ether"),("or"),("2-methoxypropane"):}`
IUPAC name of methyl-n-propyl ether is 10methoxypropane.
`H - underset(H)underset(|)overset(H)overset(|)(C ) - O - underset(H)underset(|)overset(H)overset(|)(C )- underset(H)underset(|)overset(H)overset(|)(C )-underset(H)underset(|)overset(H)overset(|)(C ) - H`
When methyl -n-propyl ether is treated with hot HI methyl iodine and propyl iodide are formed.
`CH_(3) - O - C_(3)H_(7) to Ch_(3) I + C_(3) H_(7) I + H_(2) O`